1. Field of the Invention
The invention disclosed and claimed herein generally pertains to a method and related apparatus for routing PCIe transaction packets between multiple hosts and adapters, through a PCIe switched-fabric. More particularly, the invention pertains to a method for creating and managing the structures needed for routing PCI transaction packets between multiple hosts and adapters when using a Destination Identification (DID) that is integrated into the PBA.
2. Description of the Related Art
As is well known by those of skill in the art, PCI Express (PCIe) is widely used in computer systems to interconnect host units to adapters or other components, by means of a PCI switched-fabric bus or the like. However, PCIe currently does not permit the sharing of input/output (I/O) adapters in topologies where there are multiple hosts with multiple shared PCIe links. As a result, even though such sharing capability could be very valuable when using blade clusters or other clustered servers, adapters for PCIe and secondary networks (e.g., FC, IB, Enet) are at present generally placed only into individual blades and server systems. Thus, such adapters cannot be shared between clustered blades, or even between multiple roots within a clustered system.
In an environment containing multiple blades or blade clusters, it can be very costly to dedicate a PCI adapter for use with only a single blade. For example, a 10 Gigabit Ethernet (10 GigE) adapter currently costs on the order of $6,000. The inability to share these expensive adapters between blades has, in fact, contributed to the slow adoption rate of certain new network technologies such as 10 GigE. Moreover, there is a constraint imposed by the limited space available in blades to accommodate I/O adapters. This problem of limited space could be overcome if a PC network was able to support attachment of multiple hosts to a single PCI adapter, so that virtual PCIe I/O adapters could be shared between the multiple hosts.
In order to allow virtualization of PCIe adapters in the above environment, a mechanism is required for creating and managing the structures needed for routing PCI transaction packets between multiple hosts and adapters. The mechanism must be designed so that it protects memory and data in the system image of one host from being accessed by unauthorized applications in system images of other hosts. Access by other adapters in the same PCI tree must also be prevented. Moreover, implementation of the mechanism should minimize changes that must be made to currently used PCI hardware.